arXiv subjects

D. Bazyl

Publications and source records attributed to D. Bazyl.

4 recordsLinked to original sources

arXiv2026

Design criteria for a beam-driven resonant passive transverse deflector for longitudinal beam diagnostics

Conventional radio-frequency (rf) transverse deflecting structures provide high-resolution longitudinal beam diagnostics, but require externally generated high-power rf, waveguide distribution, synchronization and input coupling at the operating frequency. We propose design criteria for a beam-driven resonant passive transverse deflector that does not require an external rf source. A leading drive bunch excites long-range wakefields in an off-axis periodic copper structure and a delayed witness bunch experiences the transverse wake near a zero crossing. The concept is based on the large temporal slope available from high-frequency wake components. A structure designed for installation after the second bunch compressor in the three-bunch-compressor layout of the European XFEL is optimized to place the zero crossing of the drive-bunch-induced transverse wake potential approximately one rf-bucket spacing of the 1.3 GHz linac, behind the drive bunch. The selected geometry produces a multi-mode transverse kick dominated by TM-like modes. We use time-domain wake simulations, frequency-domain decomposition, cell-number scaling, mechanical-tolerance scans, orbit-offset studies and uniform thermal scaling to determine the operating point and its sensitivity. For this geometry, the zero crossing occurs at s0 = 230.6 mm, with a per-cell temporal slope of Scell = 1.186 mV/(pC fs cell). For a compact 1 m structure operated with a 250 pC drive bunch and a 700 MeV witness beam, the estimated temporal resolution is about 33 fs.

physics.acc-ph↗

arXiv2026

Beam-Driven Transverse Deflecting Structure for Femtosecond Electron-Beam Diagnostics

High-resolution longitudinal phase-space (LPS) diagnostics are essential for X-ray free-electron lasers and advanced accelerators. Conventional radio-frequency transverse deflecting structures (TDSs) provide direct femtosecond-scale LPS measurements, but their substantial RF-power and infrastructure requirements strongly limit their deployment at multi-GeV beam energies. Here, we propose a beam-driven transverse deflecting structure in which a leading driver bunch, separated by one RF bucket from a trailing witness bunch under study, excites long-lived wakefields in a resonant cavity array. By placing the witness bunch near a zero crossing of the wakefield, the bunch experiences an approximately linear time-dependent transverse kick. Electromagnetic simulations of the resonant structure, combined with start-to-end beam-dynamics simulations based on European XFEL parameters at a final beam energy of 14 GeV, demonstrate a temporal resolution of $\sim 1.6$ fs for a 500 pC driver bunch, with a clear scaling toward the sub-femtosecond regime at higher charge.

physics.acc-ph↗

arXiv2025

Cathodes and Shape Modification of Cavity for DESY Superconducting Photoinjector

Four DESY prototypes of the L-band superconducting RF photoinjector cavity demonstrated on-axis peak gradients above 55MV/m during multiple vertical cryogenic tests. Two of these prototypes,16G09 and 16G10, achieved these gradients with both superconducting and normal-conducting metallic cathodes, fabricated from either high-purity niobium or lower-purity copper. The DESY photoinjector, under development for over two decades as a continuous-wave electron source for FELs, differs from other SRF injectors in that its metallic cathode plug is attached directly to the cavity backplate, exposing the emitting surface to the high electric field within the cavity. This design obviates the need for a choke filter or load-lock system. The initial 1.6-cell cavity geometry was derived from the Low-Loss design developed for the CEBAF 12GeV upgrade, scaled from 1.5GHz to 1.3GHz. This shape was later replaced with the current High Gradient TESLA profile. In this report, we discuss current cathode options and present modifications to the cavity shape aimed at significantly reducing the electric field near the cathode opening

physics.acc-ph↗

arXiv2023

High gradients at SRF photoinjector cavities with low RRR copper cathode plug screwed to the cavity back wall

In recent years we increased the typical maximum peak field on axis gradients obtained in L-band superconducting RF (SRF) photoinjector cavities at vertical tests to around 55 MV/m. This was achieved with niobium cathode plugs directly screwed to the cavity back wall omitting an RF choke filter and a load lock system for cathodes. Copper demonstrated being a suitable cathode material in normal conducting injector cavities used at X-Ray Free Electron Lasers (XFELs) operating with pulsed RF. In this article we present the first experimental confirmation that peak field on axis gradients around 55 MV/m and beyond can be achieved in L-band SRF photoinjector cavities with copper cathode plugs screwed to the cavity back wall. We view this as a major milestone for the development of a high gradient photoinjector operating continuous wave (CW).

physics.acc-ph↗